Geochemical evidence of the seasonality, affinity and pigmenation of Solenopora jurassica

Solenopora jurassica is a fossil calcareous alga that functioned as an important reef-building organism during the Palaeozoic. It is of significant palaeobiological interest due to its distinctive but poorly understood pink and white banding. Though widely accepted as an alga there is still debate over its taxonomic affinity, with recent work arguing that it should be reclassified as a chaetetid sponge. The banding is thought to be seasonal, but there is no conclusive evidence for this. Other recent work has, however demonstrated the presence of a unique organic boron-containing pink/red pigment in the pink bands of S. jurassica. We present new geochemical evidence concerning the seasonality and pigmentation of S. jurassica. Seasonal growth cycles are demonstrated by X-ray radiography, which shows differences in calcite density, and by varying δ13C composition of the bands. Temperature variation in the bands is difficult to constrain accurately due to conflicting patterns arising from Mg/Ca molar ratios and δ18O data. Fluctuating chlorine levels indicate increased salinity in the white bands, when combined with the isotope data this suggests more suggestive of marine conditions during formation of the white band and a greater freshwater component (lower chlorinity) during pink band precipitation (δ18O). Increased photosynthesis is inferred within the pink bands in comparison to the white, based on δ13C. Pyrolysis Gas Chromatography Mass Spectrometry (Py-GCMS) and Fourier Transform Infrared Spectroscopy (FTIR) show the presence of tetramethyl pyrrole, protein moieties and carboxylic acid groups, suggestive of the presence of the red algal pigment phycoerythrin. This is consistent with the pink colour of S. jurassica. As phycoerythrin is only known to occur in algae and cyanobacteria, and no biomarker evidence of bacteria or sponges was detected we conclude S. jurassica is most likely an alga. Pigment analysis may be a reliable classification method for fossil algae

Morphological and Geochemical Evidence of Eumelanin Preservation in the Feathers of the Early Cretaceous Bird, Gansus yumenensis

Recent studies have shown evidence for the preservation of colour in fossilized soft tissues by imaging melanosomes, melanin pigment containing organelles. This study combines geochemical analyses with morphological observations to investigate the preservation of melanosomes and melanin within feathers of the Early Cretaceous bird, Gansus yumenensis. Scanning electron microscopy reveals structures concordant with those previously identified as eumelanosomes within visually dark areas of the feathers but not in lighter areas or sedimentary matrices. Fourier transform infrared analyses show different spectra for the feathers and their matrices; melanic functional groups appear in the feather including carboxylic acid and ketone groups that are not seen in the matrix. When mapped, the carboxylic acid group absorption faithfully replicates the visually dark areas of the feathers. Electron Paramagnetic Resonance spectroscopy of one specimen demonstrates the presence of organic signals but proved too insensitive to resolve melanin. Pyrolysis gas chromatography mass spectrometry shows a similar distribution of aliphatic material within both feathers that are different from those of their respective matrices. In combination, these techniques strongly suggest that not only do the feathers contain endogenous organic material, but that both geochemical and morphological evidence supports the preservation of original eumelanic pigment residue

SEM images of <i>Gansus yumenensis</i> feathers and matrices.

<p>(A) MGSF317 and (B) MGSF318 matrices, and the light areas of feathers (C) MGSF317 and (D) MGSF318. Scale bars represent 4 µm.</p

Partial Py-GCMS <i>m/z</i> 57 and 55 chromatograms of <i>Gansus yumenensis</i> feathers.

<p>(A) MGSF318 and (B) MGSF317 feathers, and their corresponding matrices (C and D respectively), showing the distribution of <i>n-</i>alkane/<i>n-</i>alkene moieties. Brackets indicate an <i>n-</i>alkane/<i>n-</i>alkene doublet and the numbers indicate the carbon chain length.</p

EPR spectra of <i>Sepia officinalis</i> eumelanin, <i>Gansus yumenensis</i> and extant feathers.

<p>Samples taken at room temperature. The Gauss scale (abscissa) is approximate due to the slight variations that occur in the frequency of the incident radiation; amplitudes are arbitrary.</p

Partial ion chromatograph from the Pyrolysis GCMS of <i>Sepia officinalis</i> eumelanin.

<p>B: benzene, B1: methyl benzene, B2: ethyl benzene, Bn: benzene nitrile, Bpn: benzene propane nitrile, Py: pyrrole, Py1: pyrrole, 3-methyl, Py2: pyrrole, 2-methyl, P: pyridine, Ph: phenol, Ph1: phenol, 3-methyl, S: styrene, S1: methyl styrene, I: idole, I1: methyl indole.</p

FTIR point analyses of <i>Sepia officinalis</i> eumelanin, <i>Gansus yumenensis</i> and extant feathers.

<p>(A) Extant Marabou stork feather, (B) <i>Sepia officinalis</i> eumelanin, (C) the dark area of an isolated <i>Gansus yumenensis</i> feather (MGSF317) and its associated matrix (D). *C = O represents a group from a carboxylic acid, **C = O represents a group from either a carboxylic acid or a ketone, NĤ represents a group from a secondary amine; inorganic peaks are shown with a yellow band. (E) Shows the resultant spectra when that of the natural <i>S. officinalis</i> melanin is subtracted from that taken from the dark area of the feather. Vertical dashed lines at 1582 cm^-1 represent the C = O group of the ketone or asymmetric stretch of the carboxylic acid, and at 700 cm^-1 represents the N-H wagging group of the secondary amine, the blue band represents the OH hydroxyl group.</p

Visual and SEM images showing the presence of melanosomes in <i>Gansus yumenensis</i> and extant feathers.

<p>Isolated feathers (A) MGSF318 and (B) MGSF317, with SEM images of the fractured surfaces of (C) an extant Marabou stork feather and (D) a White-naped Crane feather, and the dark areas of MGSF317 (E-F) and MGSF318 (G-H). Eumelanosomes present within the extant Marabou stork feather (C) and the elongate mouldic structures interpreted as eumelanosomes in the fossil feathers (E-H) are highlighted with white arrows. Scale bars represent 2 cm (A-B), 5 µm (C–D) and 2 µm (E–H). The fossil feather SEM images were taken from the areas indicated by the white boxes, and the yellow dot in (B) represents the approximate area where the FTIR map discussed below is taken from.</p